Sophia Kesina, 8, of Chisholm, has a view of the wetlands from a bird hide. Photo: Graham Tidy

Ninety per cent of the fox population was waiting in reserve in case any of the top order ones died or left their territory, Dr Braysher, of the wetlands nature reserve's management committee, said. Take one out and there were many more young foxes to replace them.

Dr Braysher said research into a four-year intensive baiting program elsewhere in Australia showed no impact on fox numbers. "All that happened was a massive re-invasion," he said during one of the tours that marked World Wetlands open day at Jerrabomberra Wetlands.

This year he says there are 37 turtles' nests, and at least three pairs of foxes, but there is insufficient data to establish any long-term breeding impact.

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"We need to [collect data] for a longer time to see if there is a pattern," Mr Maconachie said. "The [turtles nesting] peak is November, they prefer rainy nights for digging, the soil is softer," he said.

Rangers are aiming to minimise feral animals' impact on the wetlands, even if means holding back on eradicating them. Their rabbit control coincides with similar work by neighbours ActewAGL's sewerage farm and Canturf's turf farm.

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"The rabbits are mainly centred on the car park ... they are not impacting on the ecological values of the site here, we just do a bit of control to keep them at manageable levels," Mr Maconachie said.

"If we did a really good job on the rabbits, the foxes are going to hammer the water birds more. If we decided to hammer the foxes just for the turtles, we would have to work out the rabbit program," he said.

Feral cats turn up in the rangers' spotlight counts, and while they eat lizards and birds, Mr Maconachie doesn't think they are as big a problem as the foxes.

"There are probably three pairs throughout the wetlands, it is rich environment, there are lots of mice and rats, lots of food. That is why there are heaps of brown snakes here, lots of birds of prey, like black-shouldered kites."

Rangers are trialling Aboriginal land management techniques like using fire, with encouraging results for turtles, which look for open areas and warm temperatures to incubate their eggs.

"So we burnt some patches just as trial, and we got three nests down in there. The foxes still got them but we know in terms of nests what are suitable environment," Mr Maconachie said.